A system and method of digital control for a blood pressure measurement system is provided. According to at least one embodiment, a photo-plethysmographic (PPG) system produces a frequency signal that corresponds to the measured light in the PPG system. Such light may be indicative of blood volume in a vein or artery. The frequency signal may be used to control one or more pressure valves of the system in order to measure blood pressure and hold the frequency signal constant.
